Embodiments of the present invention relate generally to provisional orthopedic components, and specifically, to a trial system that can be used during joint replacement surgery. The systems and methods described help a surgeon prepare a patient's bone to receive a permanent implant by providing a system that can be used to guide preparatory cuts, as well as to correctly determine the fit of the implant to be used.
The use of implant provisional components (also referred to as “trial components”) is common during joint replacement surgery. They are used to test the fit and alignment of an implant with a bone that has been reshaped by a surgeon. Although the actual implant to be used could serve these purposes, the use of trial or provisional components eliminates the risk that the actual implants will be damaged. Trial components also prevent the surgeon from having to introduce the actual components into the surgical field until the precise size of the component that will be needed is determined, saving sterilization costs and protecting the implants.
One common type of joint replacement surgery is knee surgery. In total knee joint replacement surgery, a surgeon typically affixes two prosthetic components to the patient's bone structure: a first to the patient's femur (the femoral component) and a second to the patient's tibia (the tibial component). The femoral component is typically placed on a patient's distal femur after appropriate resection, and the tibial component is typically placed on a patient's tibial plateau after appropriate preparation. Various adjustments may be made to the cuts on either the tibial or femoral surface and different component sizes are considered. During this process, the knee is flexed and extended in order to determine the appropriate size, fit, and adjustment for the components. The surgeon may interchange various trial components in order to determine the appropriate size and fit for the implant.
More specifically, trial prostheses are used for trying the fit of the actual prosthesis or implant components to respective portions of the joint. After shaping the femur and tibia, the surgeon may temporarily fit trial components instead of the actual prosthetic components to the femur and/or tibia. This enables the surgeon to test the fit and performance of the components both statically and dynamically throughout a desired range of motion. Use of trial prosthetics instead of the actual implant allows the surgeon to perform this testing and achieve a more perfect fit and a more accurate performance of the actual component without introducing the actual prosthetic components into the surgical field. Although surgeons use various imaging techniques and palpation to study a particular patient's anatomy prior to surgery, they nevertheless gain considerable information required to fit the prosthetic components after the knee has been surgically exposed and the surgery has begun.
Accurately positioning and fitting the prosthetic components is important for a number of reasons. First, each patient has a different bone structure and geometry. Also, motion of the tibia relative to the femur about every axis varies from one patient to the next. Further, some knee replacement patients may have functionality problems with medial/lateral, anterior/posterior, or varus/valgus ligaments, and an implant that constrains the movement of the knee joint may be needed to enhance stability. In these instances, the surgeon may need to use a femoral implant with a constrained box geometry to ensure stability of the knee once the ligaments have been released.
Many systems for such a cruciate ligament sacrificing procedure use a constraining box geometry cutting block/guide and a separate femoral trial in order to prepare the bone to receive a permanent implant and then test the fit. In this process, the surgeon makes the initial cut(s) using a cutting block that is placed on the femur. Such cutting blocks are typically square (i.e., they are not shaped like the actual implant) and may be secured in place on the resected femur. Anterior and posterior chamfer resections are then made to shape the bone to receive the inner portion (i.e., the “box portion”) of the femoral component. Femoral box resection cuts then need to be made. Typically, a separate femoral box cutting guide is secured on the surface of the femoral bone, and a reciprocating saw and/or box chisel is used to remove medial, lateral, and proximal (and anterior in some instances) portions of bone in the notch. Then, for trial reduction, the cutting guide is removed and a femoral trial component with box geometry built-in to the component is secured on the prepared femur. A tibial tray is placed on the prepared tibia and if necessary, a trial patellar component is also selected. Once the components are in place, the surgeon checks the range of motion and stability of the knee.
However, using a separate constraining box cutting guide and then a separate trialing component can add to surgery time, forces the surgeon to do more guessing, and is generally less efficient than if the cutting and trialing process could be accomplished with a single component. Some implant designers have attempted to solve this problem by providing variously sized adapters that can be screwed into the femoral trial component, some adapters allowing for a cruciate retaining procedure and others allowing for a cruciate sacrificing procedure. See, e.g., U.S. Pat. No. 5,776,201, issued to Johnson & Johnson Professional, Inc. on Jul. 7, 1998. Others have provided a spanning member that can be locked in place with a sliding retention member. See, e.g., U.S. Pat. No. 6,827,739, issued to Zimmer Technology, Inc. on Dec. 7, 2004. However, in order to use these systems, the femoral trial needs to be removed from the operating envelope in order to assemble the adapter or spanning member to the component, and then a reinsertion is required. In short, both of these systems cooperate with the inner or proximal portion of the femoral trial.
Embodiments of the present invention help solve these problems by providing a femoral trial component that can be used as a guide for the box cut, and that can then be completed with a cam module—without removal from the patient's bone—so that the same component can be used for the trialing process. One way this may be accomplished is by providing a cam module that can cooperate with an outer distal aspect, portion, or side of the femoral trial component so that the component does not need to be removed for trialing preparation steps.